sns

• [Core Concepts](#core-concepts)
• [Common Patterns](#common-patterns)
• [CLI Reference](#cli-reference)
• [Best Practices](#best-practices)
• [Troubleshooting](#troubleshooting)
• [References](#references)

Topics

Named channels for publishing messages. Publishers send to topics, subscribers receive from topics.

Topic Types

| Type | Description | Use Case |

|------|-------------|----------|

| Standard | Best-effort ordering, at-least-once | Most use cases |

| FIFO | Strict ordering, exactly-once | Order-sensitive |

Subscription Protocols

| Protocol | Description |

|----------|-------------|

| Lambda | Invoke Lambda function |

| SQS | Send to SQS queue |

| HTTP/HTTPS | POST to endpoint |

| Email | Send email |

| SMS | Send text message |

| Application | Mobile push notification |

Message Filtering

Route messages to specific subscribers based on message attributes.

Create Topic and Subscribe

AWS CLI:

```bash

# Create standard topic

aws sns create-topic --name my-topic

# Create FIFO topic

aws sns create-topic \

--name my-topic.fifo \

--attributes FifoTopic=true

# Subscribe Lambda

aws sns subscribe \

--topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \

--protocol lambda \

--notification-endpoint arn:aws:lambda:us-east-1:123456789012:function:my-function

# Subscribe SQS

aws sns subscribe \

--topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \

--protocol sqs \

--notification-endpoint arn:aws:sqs:us-east-1:123456789012:my-queue

# Subscribe email

aws sns subscribe \

--topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \

--protocol email \

--notification-endpoint user@example.com

```

boto3:

```python

import boto3

sns = boto3.client('sns')

# Create topic

response = sns.create_topic(Name='my-topic')

topic_arn = response['TopicArn']

# Subscribe Lambda

sns.subscribe(

TopicArn=topic_arn,

Protocol='lambda',

Endpoint='arn:aws:lambda:us-east-1:123456789012:function:my-function'

)

# Subscribe SQS with filter

sns.subscribe(

TopicArn=topic_arn,

Protocol='sqs',

Endpoint='arn:aws:sqs:us-east-1:123456789012:order-queue',

Attributes={

'FilterPolicy': '{"event_type": ["order_created", "order_updated"]}'

}

)

```

Publish Messages

```python

import boto3

import json

sns = boto3.client('sns')

topic_arn = 'arn:aws:sns:us-east-1:123456789012:my-topic'

# Simple publish

sns.publish(

TopicArn=topic_arn,

Message='Hello, World!',

Subject='Notification'

)

# Publish with attributes (for filtering)

sns.publish(

TopicArn=topic_arn,

Message=json.dumps({'order_id': '12345', 'status': 'created'}),

MessageAttributes={

'event_type': {

'DataType': 'String',

'StringValue': 'order_created'

},

'priority': {

'DataType': 'Number',

'StringValue': '1'

}

}

)

# Publish to FIFO topic

sns.publish(

TopicArn='arn:aws:sns:us-east-1:123456789012:my-topic.fifo',

Message=json.dumps({'order_id': '12345'}),

MessageGroupId='order-12345',

MessageDeduplicationId='unique-id'

)

```

Message Filtering

```bash

# Add filter policy to subscription

aws sns set-subscription-attributes \

--subscription-arn arn:aws:sns:us-east-1:123456789012:my-topic:abc123 \

--attribute-name FilterPolicy \

--attribute-value '{

"event_type": ["order_created"],

"priority": [{"numeric": [">=", 1]}]

}'

```

Filter policy examples:

```json

// Exact match

{"event_type": ["order_created", "order_updated"]}

// Prefix match

{"customer_id": [{"prefix": "PREMIUM-"}]}

// Numeric comparison

{"price": [{"numeric": [">=", 100, "<=", 500]}]}

// Exists check

{"customer_id": [{"exists": true}]}

// Anything but

{"event_type": [{"anything-but": ["deleted"]}]}

// Combined

{

"event_type": ["order_created"],

"region": ["us-east", "us-west"],

"priority": [{"numeric": [">=", 1]}]

}

```

Fan-Out Pattern (SNS to Multiple SQS)

```python

import boto3

import json

sns = boto3.client('sns')

sqs = boto3.client('sqs')

# Create topic

topic = sns.create_topic(Name='orders-topic')

topic_arn = topic['TopicArn']

# Create queues for different processors

queues = {

'analytics': sqs.create_queue(QueueName='order-analytics')['QueueUrl'],

'fulfillment': sqs.create_queue(QueueName='order-fulfillment')['QueueUrl'],

'notification': sqs.create_queue(QueueName='order-notification')['QueueUrl']

}

# Subscribe each queue

for name, queue_url in queues.items():

queue_arn = sqs.get_queue_attributes(

QueueUrl=queue_url,

AttributeNames=['QueueArn']

)['Attributes']['QueueArn']

sns.subscribe(

TopicArn=topic_arn,

Protocol='sqs',

Endpoint=queue_arn

)

# One publish reaches all queues

sns.publish(

TopicArn=topic_arn,

Message=json.dumps({'order_id': '12345', 'total': 99.99})

)

```

Lambda Permission for SNS

```bash

aws lambda add-permission \

--function-name my-function \

--statement-id sns-trigger \

--action lambda:InvokeFunction \

--principal sns.amazonaws.com \

--source-arn arn:aws:sns:us-east-1:123456789012:my-topic

```

Topic Management

| Command | Description |

|---------|-------------|

| aws sns create-topic | Create topic |

| aws sns delete-topic | Delete topic |

| aws sns list-topics | List topics |

| aws sns get-topic-attributes | Get topic settings |

| aws sns set-topic-attributes | Update topic settings |

Subscriptions

| Command | Description |

|---------|-------------|

| aws sns subscribe | Create subscription |

| aws sns unsubscribe | Remove subscription |

| aws sns list-subscriptions | List all subscriptions |

| aws sns list-subscriptions-by-topic | List topic subscriptions |

| aws sns confirm-subscription | Confirm pending subscription |

Publishing

| Command | Description |

|---------|-------------|

| aws sns publish | Publish message |

Reliability

• Use SQS for durability — SNS is push-based, SQS queues messages
• Implement retries for HTTP/HTTPS endpoints
• Configure DLQ for failed deliveries
• Use FIFO topics for ordering requirements

Security

• Use topic policies to control access
• Enable encryption with SSE
• Use VPC endpoints for private access

```bash

# Enable SSE

aws sns set-topic-attributes \

--topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \

--attribute-name KmsMasterKeyId \

--attribute-value alias/my-key

```

Cost Optimization

• Use message filtering to reduce unnecessary deliveries
• Batch operations where possible
• Monitor and clean up unused topics/subscriptions

Message Design

• Keep messages small (256 KB limit)
• Use message attributes for routing
• Include correlation IDs for tracing

Subscription Not Receiving Messages

Check:

1. Subscription is confirmed (not pending)
2. Filter policy matches message attributes
3. Target permissions (Lambda, SQS)

```bash

# Check subscription status

aws sns list-subscriptions-by-topic \

--topic-arn arn:aws:sns:us-east-1:123456789012:my-topic

# Check subscription attributes

aws sns get-subscription-attributes \

--subscription-arn arn:aws:sns:us-east-1:123456789012:my-topic:abc123

```

HTTP Endpoint Not Working

Debug:

```bash

# Check delivery status logging

aws sns set-topic-attributes \

--topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \

--attribute-name DeliveryPolicy \

--attribute-value '{

"http": {

"defaultHealthyRetryPolicy": {

"minDelayTarget": 20,

"maxDelayTarget": 20,

"numRetries": 3,

"numMaxDelayRetries": 0,

"numNoDelayRetries": 0,

"numMinDelayRetries": 0,

"backoffFunction": "linear"

}

}

}'

```

Messages Not Matching Filter

Verify:

• Message attributes are set (not in body)
• Attribute types match (String vs Number)
• Filter policy syntax is correct

```python

# Correct: attributes must be message attributes

sns.publish(

TopicArn=topic_arn,

Message='body content',

MessageAttributes={

'event_type': {

'DataType': 'String',

'StringValue': 'order_created' # This is filtered

}

}

)

# Wrong: this won't be filtered

sns.publish(

TopicArn=topic_arn,

Message=json.dumps({'event_type': 'order_created'}) # Not filtered

)

```

SQS Not Receiving from SNS

Check SQS queue policy:

```json

{

"Version": "2012-10-17",

"Statement": [

{

"Effect": "Allow",

"Principal": {"Service": "sns.amazonaws.com"},

"Action": "sqs:SendMessage",

"Resource": "arn:aws:sqs:us-east-1:123456789012:my-queue",

"Condition": {

"ArnEquals": {

"aws:SourceArn": "arn:aws:sns:us-east-1:123456789012:my-topic"

}

}

}

]

}

```

• [SNS Developer Guide](https://docs.aws.amazon.com/sns/latest/dg/)
• [SNS API Reference](https://docs.aws.amazon.com/sns/latest/api/)
• [SNS CLI Reference](https://docs.aws.amazon.com/cli/latest/reference/sns/)
• [boto3 SNS](https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/sns.html)